Method of sintering iron ore sludge



Dec. 3, 1946- w. M. STEWART l 2,412,104

' yMETHOD OF SINTERING IRON O RE SLUDGE Filed July 2', 1942 2 Sheets-sheet 1 INVENTOR. wu z /A M M- S75 WAR? By`mmctq A amv/EVS Dec. 3, 1946. w. M. STEWART METHOD OF SINTERING IRON ORE SLUDGE Filed July 2,v 1942 2 Sheets-Sheet 2 K INVENTOR. wuz/AM M. STEWART ATTORNEYS -l BY Patented Dec. 3, 1946 METHOD OF SINTERING IRON-ORE SLUDGE 4 William M. Stewart, Birmingham, Ala., assignor Y `to Republic Steel Corporation, Cleveland, Ohio,

a corporation of New Jersey -Application July 2, 1942, Serial No. 449,376

5. Claims.

Thisinvention relates generally to the art of sintering -ores or concentrateaand more partic-` ularlyto the sintering of finely divided iron ore materials containing large amounts of water.

Altho iron ore fines containing small amounts of moistureA have been sintered commercially heretofore,.no one has ever been able successfully to-sinter iron ore containing large amounts of moisture, such asriron oreA sludge, so far asl am aware. There exist quantities of` iron ore fines or concentrates in the form of sludge containing amounts of moisture ranging up to more than 20% which would yield quantities of iron if they could be sintered satisfactorily.

The difficulties in the Way of sintering such sludge-like materials, are numerous and serious. The sludge contains largeamounts of water and retains more than 20% of water which can not be removed by drainage or any other inexpensive method of separation. When. attempts are made to mix dry sintering materials. with the sludge, even that from which as much moisture as possible has been removed, the sludge forms balls with an adherent outer layer of dry material, and these balls can not be broken in the ordinary pug mill used to mix charges for the sintering machine. When dry materials containing these balls are run thru a sintering machine they are not uniformly sinteredfor the dry materials burn and sinter before the moisture can be driven out of these balls.

The present invention overcomes the previous difficulties and makes possible the economical sintering of sludge concentrates and other iron ore materials containing largeamounts of moisture.v

According to the present invention high moisture containing iron ore material, such as sludge, is spread out in thin, narrow ribbons on a thin, relatively wide, layer of substantially dry sintering materials and may also be covered with the latter. The amounts of these materials are so proportioned that the mixture will have an averagemoisture content of between about 5% and about 15%, preferably about 7%. Then these materials are thoroughly mixed and are run thru a sintering machine. In this manner the sludgelike ore or concentrates are made suitable for apparatus suitablefor. carrying-out one. step Q11 Figure 5 is a transverse` crossvsectional View;l

taken on line 5-5`of Fig.v 4.`

In Figure 1 the top reach of the endlessv belt I moves from right to left.4 hopper 2 substantially dry sintering materials,

such as flue dust, coke breeze, coal or mixturesv of vtwo or more of these. materials are spread.onto the belt in theform-of a stream 3 (Figs. 4 and. 5),v

which may be nearly as wide. as the belt. and` may range between about. 2-H and aboutv v6 iny thickness at the middle: of the belt,- where itis thickest. Asthe belt passes under the lhopper 4, screw conveyors 5 force iron ore material ccn-y taining largequantities. of moisture, suchy as sludge which, may ycontain more than, 20% of water, onto the-,stream of dry materials yon theconveyor in the ,form of: one or more ribbons, 6 which are small in cross-section and which, may' be variously shapedv in cross section andv which may, for example, be approximately 1/2," to 3/47 thick and from` 2 to- 2,1/2" wide. Altho itis not necessary, additionall substantially ldry sintering materials 1 may, if desired, be delivered on top. of the stream 3 and ribbons 6 from'hopperf. These materials may be the same as. those com-k ing from hopper 2., and makingl up the initial stream or may be one or another of lthose maf terials. f

The amounts of substantially dry 'materials discharged onto the conveyor from hoppers. 2 and 8 are so proportioned with respect to the. amount' of iron ore materials discharged vfrom the screw conveyors 5 that the average moisture content of the combined materials. will be the amount desired for good sintering practice, ranging` from. about 5% to about 15%, usually about 7%..

The materials 3, 6 and 1 on belt I maybe discharged into the hopper 9" from whichthey-may be transferred, as by conveyor I0 to amixing drum or pug mill II in. which they areithoroughfl ly and uniformly mixed. Then `the;mixture:51s; discharged into a hopper I2 and fed onto the pallets I3 of a sintering machine indicated diagrammatically at I4, and finally the sintered material is discharged into hopper I5.

Figs. 2 and 3 show in some detail the hopperv 4 and screw conveyors 5 of Fig. 1. The hopper 4 has a top opening into which wet iron ore or 22. These conveyors are enclosed by housings 20, are supported in bearings 23, and are rotated by chains ,A24 25. Each housing has a valve controlledf'outletl, the two outlets being staggered sothat'thetwo ribbons 6 will not overlap each other on belt I.

Preferably, means are provided for tempering the sludge, that is, adjusting the consistency of various lots to a standard or uniform amount of moisture. water line 30 with connections 3| and 32 to the interior of the housing 20 and hopper 4. Usually little or no water need be added by this means. Y

While screw conveyors of dill'erent capacities may obviously be employed, success has been had with screw conveyors which had a capacity of about 20,000 pounds per hour of material weighing about 120 pounds per cubicv foot and containing about 221A1% of moisture when the screws rotated atvabout 80 R. P. M. These screws were about 6 in outside diameter with a 3" pitchvand the openings 26 were of the sizes above stated. By adjusting the size ol openings 26 at the discharge end of the housings' 20 the thickness of the ribbons 6 of material delivered onto the stream of material on the belt conveyor I can be regulated las desired.j l

--It willbe understood that when the ribbons of sludge are'laid on the dry lines on the belt, the iln'es which'contact with the ribbons adhere thereto and absorb some moisture therefrom. A similar raction takes place if and when dry nes are delivered onto the ribbons. When the materials are vdischarged from the belt the ribbons breakup into short lengths and more dry fines adhere to the thus exposed surfaces thereof. This laction isv repeated while the material is being conveyed to the pug mill, while it is being tumbled therein andr when it is discharged into and thru the hopper onto the pallets. As a. result of starting with thin narrow ribbons of sludge onv dry fines amounting to several times the volume ofthe sludge, and treating the mixture as described, the sludge reaches the pallets in 'the form' of uniformly divided particles which have been partly dehydrated by the dry lines and which are thoroughly mixed with combustible fines. These piecesare quickly dried out and are readily ignited and sintered on the sintering machine.- Y

It will be understood that the use of the screw conveyor makes it vpossible to proportion the amount of iron bearing materials, such as ore or concentrates, which is added tothe other materials. In other words, the percentage of such iron bearing material as well as the percentage of the iron-values themselves in the sintering mixture may be closely controlled by the method'ol?` this invention."` Y

Having thus described my invention so that others skilled in the art may be'V able to understand and practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

As illustrated, this means includes a'v What is claimed is: f

1. The method of sintering which includes the steps of moving sintering material having a low moisture content forwardly in the form of a stream, depositing on said moving stream a thin. relatively narrow ribbon of iron bearing material having a small cross-sectional area and a high moisture content and thereby transferring some of the moisture of the high moisture material to the low moisture materials, and so prof portioning the amounts of said materials that the moisture content of the mixture will be between 'about 5% and about 15%, thoroughly mixing said materials, and sintering the resulting mixture.

2. The method of sintering which includes the steps of moving sintering material having a low moisture content forwardly in the form of a relatively small cross-section stream, depositing on said moving stream a plurality of thin, spaced apart, ribbons of material having a high moisture content, and spreading additional sintering material of low moisture Vcontent on said moving materials, and thereby transferring some of the moisture of the high moisture. material to the low moisture materials thoroughly mixing said materials, and sintering the resulting mixture.

3. The method of sintering which includes thev steps of moving substantially dry sintering vmaterial forwardly in the form of a stream, depositing on said moving stream a plurality of relatively thin and narrow ribbons of iron ore materials having a moisture content of above aboutA 20%', and spreading sufficient, additional, substantially dry, sintering material onsaid moving materials to bring the' moisture content of the mixture of said materials to between about 5% and about 15% While preventing the iiowof substantial quantities of gas thru said materials, thoroughly mixing said materials, and sintering the resulting mixture.

4. The method of sintering. which includes the steps of moving sintering material having a low moisture content forwardly'` in. the form of a stream, depositing'on said moving stream. in the form of a thin, relatively narrow ribbon, a quantity of iron ore material having a high moisture extruded material onto said movingstream and so proportioning the amounts of said materialsv that the moisture content of the mixture will be between about 5% `and about 15%,'thoroughly mixing said materials, and sintering the result-` ing mixture. y

Y i WILLIAM M. STEWART.Vv 

